Diagnostic catheters are employed for the diagnosis of patients with coronary insufficiency, more specifically, with ateriosclerosis (arteriosclerosis caused by atheromas). The diagnostic catheters typically consist of specially configured tubes to allow their introduction into the coronary arteries and to enable the injection of a contrast fluid for x-rays of the coronary arteries. While contrast fluid is injected, radiographic pictures are taken to detect the possible obstruction points of the arteries, which result from the atheroma process.
If an obstruction is verified, this may lead to a medical procedure called a coronary transluminal angioplasty, which involves removing the obstruction from the blocked artery to improve blood flow. According to this procedure, a special tube is first placed in the patient, which is called a guide catheter, and, through the guide catheter, a fine wire is introduced, called the guide wire, which moves through the obstructed part of the compromised artery to be treated. Then, taking advantage of the guide wire, a second or balloon catheter slides over the guide wire. The end of the balloon catheter is equipped with a balloon, which is positioned along the entire obstructed section of the artery. The balloon is then inflated, one or more times, pressing the atheromas against the wall of the blood vessel or artery. Thus, the diameter of the vessel is increased, and the flow of blood is improved. Once the artery is disobstructed, the balloon catheter and the guide wire are removed. A radiographic image using contrast is then obtained of the disobstructed artery observe the result. Finally, the guide catheter is removed, completing the coronary angioplasty.
Unfortunately, it is not uncommon after the balloon angioplasty to observe a new reduction of the caliber of the blood vessel that has been treated. More so recently, in order to reduce the risk of a new obstruction forming, the coronary angioplasty has been accompanied by an additional procedure, the implantation of a device called the coronary stent.
A stent device is configured using a metallic tube, the wall of which is formed by a mesh of flexible metallic wires which are conveniently doubled and interconnected among themselves. In an initial position, the mesh, or rather, the folds of its wires, are absolutely closed, so as to form a tube with a rather reduced diameter. The mesh of metallic wires, which forms the wall of the stent, is capable of being unfolded, so as to bring about the radial expansion of the tube. This radial expansion is provoked by the inflation or insufflation of a balloon that is previously adhered to the stent along its entire length.
Thus, during the coronary angioplasty procedure described above, as soon as the disobstruction of the artery has been concluded, another balloon catheter equipped with the coronary stent discussed above is introduced into the artery. Once the stent is positioned along the recently disobstructed section or stretch, the balloon is inflated, which causes the radial expansion of the stent. The wall of the stent, with the metallic wires now expanded, further presses the atheroma plaque against the wall of the blood vessel, which has already been pressed by the first or previous balloon catheter. Once expanded, the stent is released from the balloon, and adheres to the vessel, and the balloon catheter which expanded the stent is removed, leaving only the stent.
The devices and the techniques normally used in the procedure to disobstruct compromised arteries (with ateriosclerotic lesions) have proven to be relatively efficient in a large number of the cases. However, when the ateriosclerotic lesions agglomerate at the origin of lateral arterial branches, or when they are localized in arterial bifurcations of the coronary circulation system, the implantation of stents frequently raises concerns. Until now these concerns have yet to be solved, whether for the obstruction of a lateral branch or for lesions formed in arterial bifurcations. These concerns result from the compression of the atheroma plaque against the wall of the blood vessel upon expansion of the stent. This may cause the reduction in the caliber of the opening that provides access to the secondary branch (ostium of the branch), and often results in total obstruction. In this case, the stent becomes a potential impediment to the passage of any disobstruction element or device for the ostium.
This invention is directed to a device having a conventional balloon catheter, the balloon of which supports a stent arranged in accordance with the principles of the present invention. The stent does not totally adhere to the balloon along the length of the stent. The stent has two sections. One section, which is preferably approximately two thirds of the total length of the stent, is firmly adhered to the balloon, as provided for in conventional stents. The other section, preferably corresponding to the other third of the length of the stent, does not adhere to the balloon and is partially expanded before its use, so as to enable passage through the mesh of an appropriate metallic guide wire. This metallic wire is previously introduced into a secondary branch or bifurcation in proximity to the obstruction. In the case of lesions located in proximity to arterial bifurcations, the guide wire leads to one of the branches, and will serve to guide the second balloon to the ostium of the branch. The metallic wire enables a second stent or a second angioplasty balloon to be introduced after disobstructing the main artery through the traditional method of coronary angioplasty and stent placement, if the second branch or bifurcation becomes blocked.
During the disobstruction of the main artery by the traditional method of coronary angioplasty and stent implantation, the secondary artery may become blocked. In other words, the subject invention maintains through the mesh of the new device a stationary wire in the secondary branch. This wire may be used as an access to the secondary branch if necessary and enables introduction of an element having a second balloon or stent for the disobstruction of the ostium.
This invention is also directed to a new method for implanting a stent. Although it includes some procedures already employed in the traditional method of coronary angioplasty followed by the implanting of the stent, the subject invention presents a sequence of new procedures and interferences, capable of permitting the adequate use of the new device.